1. Field of the Invention
The present invention relates to a pumping device particularly suited for insertion into a drum or other similar container.
2. Description of the Prior Art
As shown in the specification and the drawings of U.S. Pat. No. 3,094,938, a pumping device is disclosed having a reciprocating pump below a reciprocating actuator driven by pressurized working fluid.
The diameters of a working piston of the reciprocating actuator and a working piston of the reciprocating pump of the above pumping device are identical.
With the above type of pumping device, one way to increase pump output pressure is to make the diameter of the working piston of the reciprocating pump smaller than that of the working piston of the reciprocating actuator.
In that case, it may be convenient to use a pump piston which vertically moves in the pump cylinder below the working rod of the reciprocating actuator with a pump rod having a smaller diameter than the working rod in between, since then there is no need to modify the structure of the reciprocating actuator.
This construction has a problem in finding a way to vent the enclosed space, in which the working rod of the reciprocating actuator moves up and down, to the outside.
Especially in the case where the reciprocating pump is inserted into a drum so that only a small portion of the pumping device protrudes from the can, the space in which the working rod moves vertically (hereinafter called the working rod vertical movement space) is also inside the drum. Therefore, simply boring a hole in the cylinder is not effective to vent the enclosed space surrounding the movement space surrounding the working rod vertical to the outside.
Since the above problem has not yet been solved, a conventional pump calls for the entire body of the reciprocating actuator and the reciprocating pump to project outside the drum, as shown in the specification and the drawings of said U.S. Pat. No. 3,094,938. In addition, this problem makes it impossible to employ a two-stage rod system to increase the pump output pressure.